Connecting precast concrete structural members

ABSTRACT

This invention is directed to a connection assembly for joining precast structural members together wherein metal members are provided on the structural members and which are attached to reinforcements in the said structural members, said metal members having taper formations thereon engaging corresponding formations in end clamp members adapted to be drawn together to effect engagement of outer faces of the metal members with a central shaft passing through the connection assembly and cooperating with the end clamp members, the arrangement providing for a column supported or unsupported connection through which the whole of the moment forces are transferred.

United States Patent [72] Inventor Stewart George Pinniger l3 FairviewStreet, Hawthorn, Victoria, Al-Btl'llifl [21] Appl. No. 825,859

[22] Filed May 19, 1969 [45] Patented June 22, 1971 [54] CONNECTINGPRECAST CONCRETE 584, 726, 693, 253, 251, 260, 280, 295, 300, 225, 223,587;287/lll,1l8, 189.36 C

[56] References Cited UNITED STATES PATENTS 1,024,852 4/ 1912 Holmberg52/583 3/1952 Henderson Primary Examiner-Price C.' Faw, Jr.Attorney-Oberlin, Maky, Donnelly & Renner ABSTRACT: This invention isdirected to a connection assembly for joining precast structural memberstogether wherein metal members are provided on the structural membersand which are attached to reinforcements in the said structural members,said metal members having taper formations thereon engagingcorresponding formations in end clamp members adapted to be drawntogether to effect engagement of outer faces of the metal members with acentral shaft passing through the connection assembly and cooperatingwith the end clamp members, the arrangement providing for a columnsupported or unsupported connection through which the whole of themoment forces are transferred.

PATENTFUJUNPPIS?! 3.585771 sum 2 OF 3 l 16m?" Lilnlwuq CONNECTINGPRECAST CONCRETE STRUCTURAL MEMBERS structural members. Another knownmeans of locking beams I to a column support involves the use ofclamping dogs which engage plates attached to beam reinforcements tohold members in conjunction against a spacer block. This method cannotbe used to transfer full moment forces through the connection and theconnection may be made only at points of support. Known methods usuallyrequire subsequent grouting or encasing the connection with concrete andonce erected, members cannot be readily dismantled for reerection.

Reinforced concrete structural beams or columns are hereinafter referredto as beams or columns or collectively as structural members.Reinforcements may be metal bars or prestressing wires or tendons andare hereinafter referred to as reinforcements.

The principal object of the present invention is to provide a relativelysimple and economical means of effecting a connection between two ormore beams or between two or more beams and a column, which is capableof transferring the whole of the moment forces through the connection,which permits subsequent disconnection and which involves a minimum ofonsite work for either operation.

According to the invention, a connection for structural members includesthe provision of metal sections at the ends or within recesses formed inthe members, said sections being attached to the reinforcements in themembers by welding or anchoring and having formations thereon to engageupper and lower clamp members adapted to draw out surfaces of the metalsections of the structural members connected into engagement with acentral clamp shaft passing through the connection assembly.

The outer surfaces of the metal sections are formed as segments of ashape to match that of the central shaft passing through the connectionassembly. The clamp members are provided with holes through which theclamp shaft passes and said clamp members may be drawn together by,meansof a nut or nuts engaging with a screw thread or threads at one or bothends of the shaft. Alternatively, they may be drawn together by a boltthrough a hole in the shaft.

The engaging surfaces of the metal sections and clamp members areinclined to the direction of the clamp pressure to provide an initialtolerance for the engagement of the ends of metal sections with theclamp members. As the clamp members are drawn together, the metalsections are forced in wardly together and locked to the central shaftwhen the clamp members are fully engaged.

When a connection of one or more beams to a supporting column isrequired, the lower clamp member of the central shaft are attached tothe column reinforcements which are welded or anchored to said clampmember.

Where a simple connection is required between two beams away from apoint of support, one or more connectors may be used in a horizontal orvertical position with the metal sections projecting at the sides of thebeam ends.

The clamp connection may be employed for the transfer of stress from adiagonal member to another diagonal member or members or to a horizontalor vertical member or members as may be required in a braced structure.

A column junction may be formed by locating two or more connectors in ahorizontal position at right angles to the column axis.

In one arrangement, the reinforcements of the beams are welded at theirends to metal sections adapted to form with other metal sections,segments of a hollow round bar, tapered externally at each end. Thesegments are positioned against a central shaft matching the internaldiameter of the hollow round bar. The projecting ends of the segmentsengage in a circular recess in each of the clamp members which matchesthe external diameter and taper at the ends of the hollow round bar ofwhich the segments form part. The ends of the central shaft are providedwith threads and the clamp members are drawn closer together by means ofnuts engaged on the threads.

In another arrangement, where the reinforcements comprise prestressingtendons, the latter pass through apertures in the metal sections intowhich they are anchored. In this case, the external faces of the metalsections are shaped to provide sufficient area to spread compressiveforces due to tensioning and subsequent loading, so that these arewithin the designed compressive strength of the concrete.

The profile of the metal section is shaped to provide sufficientstrength to transfer bending stresses from the prestressing tendons tothe upper and lower clamp plates.

In order that the invention may be more readily understood referencewill now be made to the accompanying drawings illustrating practicalembodiments of connections for structural members constructed accordingto the present invention. In these drawings:

FIG. I is a vertical section through a clamp connection between twoopposite beams, and a column cast in reinforced concrete;

FIG. 2 is a fragmentary perspective connection assembly as it wouldappear without concrete encasement;

FIG. 3 is a vertical section through a clamp connection between twoopposite beams, and a column in which the beams and column are in oneform of prestressed concrete;

FIG. 4 is a fragmentary perspective of one segment engaged in a lowerclamp plate to further illustrate FIG. 3;

FIG. 5 is a plan showing four beams with connection as shown in FIG. 3with clamp plate removed;

FIG. 6 is a fragmentary perspective of the end of a concrete beamshowing a segment, the ends of which project to engage in recesses inthe clamp plates;

FIG. 7 is a section through one end of the connection showing a clampplate at point of engagementwith one end of a segment;

FIG. 8 is a similar section showing a clamp plate fully engaged andlocked with a nut;

FIGS. 9 and 10 are diagrammatic elevations of end connections betweenbeam ends employing one or more connectors as illustrated in FIGS. l to8;

FIG. 11 is a diagrammatic elevation of a connection between a beam andtwo diagonal members;

FIG. I2 is a diagrammatic elevation of a connection between a beam and acontinuous column; and

FIG. 13 is a diagrammatic elevation of a column connection.

FIGS. 1 and 2 illustrate the connection between the ends of two beams 14on a supporting column 15. The connection assembly comprises metalsections 16, in the form of segments of a hollow round bar, and whichare attached, by welding, to the ends of reinforcing bars 17 cast in thebeams 14. Said sections 16 are positioned at the ends of the beams 14and extend centrally for the major portion of the end face 18 in whichthey are cast to form upper and lower stepped portions 19 at the ends ofthe beams. The ends 20 of the sections I6 extend past the steppedportions 19 and have tapered formations 21 adapted to engage acorresponding tapered face 22 in recesses 23 in upper and lower clampplates 24 and 25 which are acbeams to be connected together.

The clamp plates 24 and 25 are each provided with a central aperture 26to receive a clamp rod or bar 27 which is threaded at least at the outerend to receive a clamp nut 28. The other or inner end of the clamp rod27 is shown as threaded to receive a securing nut 29 for fixing the rod27 in the column 15. Where the connection assembly is to be used toconnect the ends of two beams together both ends of the clamp rod 27 arethreaded to receive clamp nuts for closing the clamp plates 25 and 26onto the sections 16.

As illustrated in FIGS. 1 and 2 the connected ends of beams 14 aresupported on the lower clamp plate 25 which is formed with projections29 which are welded to the reinforcements 30 in the column. The innerend of the clamp rod 27 extends into the concrete at the top of thecolumn and is bolted by nut 29 to a securing plate 31 which is alsowelded to the reinforcements 30.

It will be noted that the inner, exposed faces of the metal sections 16bear on the surfaces of the clamp rod 27 throughout a substantialportion of the length of the rod, thereby to provide an effectivetransfer of the moment forces.

The clamp rod 27 may be of rectangular or hexagonal cross sectioninstead of circular as illustrated and in these cases the faces of.sections 16 engaging the clamp rod are correspondingly shaped to bear onthe clamp rod. In another arrangement (not shown) the clamp rod may beprovided with a sleeve, the outer faces of the sections 16 being adaptedto bear upon the sleeve.

The faces 22 of the recesses 23 in the clamp plates 24 and 25 engage thetapered formations 21 of the extending ends of the sections 16 on thebeams 14 to be connected together so that whenthe clamp plates are drawntogether by tightening the nuts at one or both ends of the clamp rodcompression forces are transferred through the connection by the innerfaces of the sections bearing on the clamp rod or sleeve thereon.Tension forces are transferred by the inner faces of the extending endsof the sections bearing on the recesses in the clamp plates. Where theclamp rod forms part of a column, continuity is provided in theconnection between the beams and the column.

FIGS. 3 and 4 are views similar to FIGS. 1 and 2 illustrating a similarconnection assembly parts of which are modified to enable prestressedreinforcements tendons to be anchored thereto. In this arrangement thebeams 140 have incorporated therein prestressed tendons 17a which passthrough apertures 16b in the metal sections 160, recesses 16c thereinbeing provided to accommodate the anchoring heads 17b of the tendons17a.

In order to compensate for the weakening of the metal sections 164 bythe apertures 16b and recesses 16c, the sections are shouldered as at16d or provided with reinforcing webs to spread compressive forces dueto tensioning and subsequent loading and to resist bending momentswithin the lengths of the section 16a.

The lower clamp plate a is provided with recessed apertures 25b toreceive the ends and anchoring heads b of prestressed reinforcingtendons 30a in column 15a.

The clamp rod 27a in this arrangement is directly secured to the lowerclamp plate 25a by nut 29a engaging a threaded end on rod 27a. Toprovide rigidity between the clamp rod and clamp plate, the shoulder endof the clamp rod 27a is tapered as at 27b to seat in a correspondingtapered recess 25c in the clamp plate 25a.

The upper clamp plate 24a is the same as that illustrated in FIGS. 1 and2 and is secured in a similar manner to that previously illustrated.

It will be apparent that beams or column having reinforcements bars 17and 30 may bejoined to beams or columns having prestressing tendons 170or 30a, that is reinforced or prestressed structural members may be usedand connected together in any arrangement required.

Furthermore, holding down bolts (not shown) may be cast in beams toproject from the upper faces thereof to secure thereto the baseplates(not shown) of columns supporting upper floor or roof structures.

FIG. 6 is a view illustrating the metal section 16a at one end of a beam14a the end of which is shaped to nest with and be connected to othersimilar beams on a supporting column as shown in plan in FIG. 5.

To effect a connection between beams and a column, the ends of the beamsare positioned with the lower tapered ends of the segments engagedwithin the matching tapered recess in the lower clamp plate which isattached to the top of the column. The weight of the beam causes thesegments to drop into the recess and the taper forces the outer faces ofthe segments into close contact with the lower end of the clamp shaft.

Under normal conditions compressive forces will act at the lower end ofthe connection and tensile forces will be transferred through the upperclamp plate. However, under some design conditions a reversal of loadingwill induce tension through the lower clamp plate.

FIG. 7 shows an upper clamp plate 24 or 24a which is used to completethe connection, and is shown in a position to engage the upper ends ofthe sections 16 or 16a. Due to deflection or inaccuracies, the lattermay not be in close initial contact with the upper end of the clampshaft 27 or 27a. However, the taper on the upper ends of the sections 16or 16a and within the recess in the upper clamp plate 24 or 24a aredesigned to provide sufficient tolerance to enable the lower edge of theclamp plate recess to fit over the upper ends of the sections 16 or 16aif these are slightly displaced. The clamp plate is then forced downwardby means of the clamping nuts on the threaded upper end of the clampshaft 27 or 27a, forcing the ends of the section tightly against theshaft.

FIG. 8 shows the upper clamp plate fully engaging the upper ends of thesegments which have been forced laterally against the clamp plate andlocked in this position.

If necessary the clamp plates may be forced closer together by hydraulicor mechanical pressure means and then looked with the nut.

FIGS. 9 to 13 diagrammaticallyillustrate typical arrangements forconnecting various structural members together by clamp assemblies asillustrated in FIGS. 1 to 3, the clamp assemblies in these views beingdiagrammatically represented as 31 in each Figure.

FIG. 9 illustrates the unsupported connection of the ends of two beams Aand B by one clamp assembly 31. FIG. 10 illustrates the unsupportedconnection of two deeper section beams C and D by two clamp assemblies31.

FIG. 11 shows the connection of two bracing members E and F to a beam Gby a clamp assembly 31. FIG. 12 shows the connection of a beam H to ashouldered column I by a clamp assembly 31 and FIG. 13 shows aconnection by two clamp assemblies 31 between two column sections .I andK.

In all views FIGS. 9 to 13 the clamp assemblies 31 are shown as beinglocated in a horizontal plane, however, the assemblies in FIGS. 9 and 10may be disposed in a vertical plane. The metal sections forming part ofthe clamp assemblies, when located in the side of a structural member,as shown in FIGS. 1 l and 12 are located in recesses in the member andare attached to the reinforcements in the associated member.

What I claim is:

l. A connection assembly for concrete precast structural memberscomprising a. metal sections positioned at the adjoining ends of atleast two structural members and rigidly secured thereto, said metalsections extending substantially through said structural members andbeing formed with tapered end portions,

b. clamp members adapted to be disposed over said tapered end portionsof said metal sections, said clamp members being formed with taperedportions corresponding to said tapered end portions of said metalsections and adapted to engage the same when the structural members areclamped together,

c. a clamp shaft passing through the assembly between said metalsections and contiguous thereto throughout at least a substantialportion of the length of said shaft, said shaft having opposed endsextending beyond said clamp members, and

' d. means associated with the opposed ends of said shaft forclamping'said clamp members to said metal sections to draw the sametogether thereby effecting locking engagement of the outer surfaces ofsaid metal sections to said clamp shaft.

2. The connection assembly of claim 1 wherein at least one of the clampmembers is provided with an opening through which the clamp shaft passesand a thread on at least one end of the clamp shaft to receive a nut fordrawing the clamp members together.

3. The connection assembly of claim 2 wherein the end clamp members haverecesses therein to receive and engage matching formations on the metalsections and with the engaging surfaces on the clamp members metalsections being inclined to the direction of clamping pressure so as toeffect engagement of the metal sections and the clamp shaft.

4. The connection assembly of claim 1 wherein the outer surfaces of themetal sections are formed as segments of a shape to engage that of theclamp shaft.

5. The connection assembly of claim 1 for providing a connection of atleast one beam to a supporting column including column reinforcementswherein one clamp member is fixed to the column reinforcements and theclamp shaft is attached to the column reinforcements.

6. The connection assembly of claim 5 wherein the clamp shaft isindirectly attached to the column reinforcements by being fixed to theclamp member attached to said column reinforcements.

7. The connection assembly of claim 5 wherein the one clamp member iswelded to the column reinforcements and the clamp shaft is bolted to asecuring plate welded to said reinforcements.

8. The connection assembly of claim 5 wherein the one clamp member isprovided with recessed apertures to receive anchored ends of the columnreinforcements and the said clamp member is provided with a taperedrecess to receive a correspondingly tapered shoulder end on the clampshaft which is secured to said clamp member by a nut on a threadedextension in the clamp shaft.

9. The connection assembly of claim 1 wherein the metal sections areprovided with recessed apertures in which prestressed reinforcements areanchored, said metal sections being provided with reinforcing shouldersto spread compressive forces due to tensioning and subsequent loadingand to resist bending movements within the length of the section.

10. The connection assembly of claim 1 further including reinforcementmembers in said structural members, said metal sections being rigidlysecured to said reinforcement members.

1. A connection assembly for concrete precast structural memberscomprising a. metal sections positioned at the adjoining ends of atleast two structural members and rigidly secured thereto, said metalsections extending substantially through said structural members andbeing formed with tapered end portions, b. clamp members adapted to bedisposed over said tapered end portions of said metal sections, saidclamp members being formed with tapered portions corresponding to saidtapered end portions of said metal sections and adapted to engage thesame when the structural members are clamped together, c. a clamp shaftpassing through the assembly between said metal sections and contiguousthereto throughout at least a substantial portion of the length of saidshaft, said shaft having opposed ends extending beyond said clampmembers, and d. means associated with the opposed ends of said shaft forclamping said clamp members to said metal sections to draw the sametogether thereby effecting locking engagement of the outer surfaces ofsaid metal sections to said clamp shaft.
 2. The connection assembly ofclaim 1 wherein at least one of the clamp members is provided with anopening through which the clamp shaft passes and a thread on at leastone end of the clamp shaft to receive a nut for drawing the clampmembers together.
 3. The connection assembly of claim 2 wherein the endclamp members have recesses therein to receive and engage matchingformations on the metal sections and with the engaging surfaces on theclamp members metal sections being inclined to the direction of clampingpressure so as to effect engagement of the metal sections and the clampshaft.
 4. The connection assembly of claim 1 wherein the outer surfacesof the metal sections are formed as segments of a shape to engage thatof the clamp shaft.
 5. The connection assembly of claim 1 for providinga connection of at least one beam to a supporting column includingcolumn reinforcements wherein one clamp member is fixed to the columnreinforcements and the clamp shaft is attached to the columnreinforcements.
 6. The connection assembly of claim 5 wherein the clampshaft is indirectly attached to the column reinforcements by being fixedto the clamp member attached to said column reinforcements.
 7. Theconnection assembly of claim 5 wherein the one clamp member is welded tothe column reinforcements and the clamp shaft is bolted to a securingplate welded to said reinforcements.
 8. The connection assembly of claim5 wherein the one clamp member is provided with recessed apertures toreceive anchored ends of the column reinforcements and the said clampmember is provided with a tapered recess to receive a correspondinglytapered shoulder end on the clamp shaft which is secured to said clampmember by a nut on a threaded extension in the clamp shaft.
 9. Theconnection assembly of claim 1 wherein the metal sections are providedwith recessed apertures in which prestressed reinforcements areanchored, said metal sections being provided with reinforcing shouldersto spread compressive forces due to tensioning and subsequent loadingand to resist bending movements within the length of the section. 10.The connection assembly of claim 1 further including reinforcementmembers in said structural members, said metal sections being rigidlysecured to said reinforcement members.